Slider
textsize.addChangeListener(new ChangeListener()
    public void stateChanged(ChangeEvent e)
         numbersize.setText("" + ((JSlider)e.getSource()).getValue());
);

String wielkosc_string = numbersize.getText();
wielkosc = Integer.parseInt(wielkosc_string);


FileChooser
JFileChooser wybor = new JFileChooser();
    if(wybor.showOpenDialog(null) == JFileChooser.APPROVE_OPTION)
        File selectedFile = wybor.getSelectedFile();

PrintWritter
PrintWriter zapisz;
try
  zapisz = new PrintWriter("plik.txt");  
  zapisz.println(wpisz.getText()); 
  zapisz.close();
catch (FileNotFoundException ex)
   Logger.getLogger(okno.class.getName()).log(Level.SEVERE, null, ex);


try
  Scanner odczyt = new Scanner(plik);
  String tekst = odczyt.nextLine();
  wyswietl.setText(tekst);
              
  catch (FileNotFoundException ex)
	Logger.getLogger(okno.class.getName()).log(Level.SEVERE, null, ex);